Field of the Invention
The present invention relates to an arrow, and more particularly to an arrow having an improved function.
Background Art
In general, when an arrow is fired by a bow, it is instantaneously subject to a strong propelling force by a string.
At this time, since the string is acted upon by an inertia force which intends to keep a standstill condition at a present position, in general, when the arrow is fired by the bow, it is instantaneously subject to the strong propelling force by the string.
At this time, since the string is acted upon by the inertia force which intends to keep the standstill condition at the present position, the inertia force and the propelling force act on the arrow.
Since the inertia force acts on the entire arrow and the propelling force acts on a rear end of the arrow and is transmitted to a fore end thereof, a deflection deformation is generated at a middle of the arrow.
The magnitude of the deflection deformation varies with an elastic force of the bow and a length by which the string is drawn. If a strength of the bow is large or the length by which the bow is drawn is large, the arrow is deflected large, and if a strength of the bow is weak or the length by which the bow is drawn is small, the arrow is deflected small, and the deflection is a very important factor in firing of the arrow.
That is, the stronger the bow and the longer the length by which the bow is drawn, the strength of the middle portion of the arrow must be large.
In consideration of this, conventionally about 12 to 14 kinds of size of the arrow are manufactured by forming a fore end portion and a rear end portion of the arrow to have a constant thickness and forming a diameter of a middle portion to be large.
However, in case where the diameter of the middle portion of the arrow is large, a center of weight is positioned at the middle portion of the arrow, and accordingly there occurs a problem in that athletes requiring a high degree of accuracy must use an expensive tungsten point of high specific gravity to further shift the center of weight forward.
Furthermore, if the arrow is cut to suit the length of arms of a user, there occurs a problem in that it is impossible to adjust the degree of the deflection of the arrow as much as required.
In the two cases described above, there is a disadvantage in that since the thickness and the outer diameter become diverse according to the kinds of the arrow, a nock and the point have to be selected among 12 to 14 kinds accordingly. In case where the length of the middle portion of the arrow is increased, the arrow has a taper shape in which the diameter is gradually decreased going toward the fore end portion and the rear end portion from the middle portion.
In this case, when a part of the fore end portion or the rear end portion of the arrow is cut to adjust the length of the arrow, there occurs a problem in that the position of the end of the fore end portion or the rear end portion before the cutting comes close to the middle portion of the arrow, whereby the diameter is increased so that the point or the nock which could be combined before the cutting may not be combined.